High density data storage medium, method and device

ABSTRACT

A composition of matter for the recording medium of nanometer scale thermo-mechanical information storage devices and a nanometer scale thermo-mechanical information storage device. The composition includes: one or more polyaryletherketone polymers, each of the one or more polyaryletherketone polymers having two terminal ends, each terminal end having two or more phenylethynyl moieties. The one or more polyaryletherketone polymers are thermally cured and the resulting cross-linked polyaryletherketone resin used as the recording layers in atomic force data storage devices.

FIELD OF THE INVENTION

The present invention relates to the field of high-density data storageand read-back and more specifically to a data storage and read-backmedium, a data storage and read-back system, and a data storage andread-back method.

BACKGROUND OF THE INVENTION

Current data storage and imaging methodologies operate in the micronregime. In an effort to store ever more information in ever-smallerspaces, data storage density has been increasing. In an effort to reducepower consumption and increase the speed of operation of integratedcircuits, the lithography used to fabricate integrated circuits ispressed toward smaller dimensions and denser imaging. As data storagesize increases and density increases and integrated circuit densitiesincrease, there is a developing need for compositions of matter for thestorage media that operate in the nanometer regime.

SUMMARY OF THE INVENTION

A first aspect of the present invention is a composition of matter,comprising: one or more polyaryletherketone polymers, each of the one ormore polyaryletherketone polymers having two terminal ends, eachterminal end having two or more phenylethynyl moieties.

A second aspect of the present invention is a method, comprising:forming a layer of the one or more polyaryletherketone polymers of thefirst aspect on a substrate; thermally curing the one or morepolyaryletherketone polymers of the first aspect to form apolyaryletherketone resin, the polyaryletherketone resin cross-linked bycyclo-addition reactions of the phenylethynyl moieties; heating andbringing a thermo-mechanical device into contact with thepolyaryletherketone resin to write information into thepolyaryletherketone resin; bringing the thermo-mechanical device, whenunheated, into proximity to the polyaryletherketone resin to readinformation stored in the polyaryletherketone resin; and heating andbringing the thermo-mechanical device into proximity with thepolyaryletherketone resin to erase information from thepolyaryletherketone resin.

A third aspect of the present invention is a method, comprising: forminga layer of polyaryletherketone resin on a substrate by thermally curingone or more polyaryletherketone polymers, each of the one or morepolyaryletherketone polymers having two terminal ends, each terminal endhaving two or more phenylethynyl moieties, and bringing athermal-mechanical probe heated to a temperature of greater than about100° C. into proximity with the layer of a polyaryletherketone resinmultiple times to induce deformed regions at points in the layer of thepolyaryletherketone resin, thereby writing information in the layer ofthe resin.

A fourth aspect of the present invention is a data storage device,comprising: a recording medium comprising a layer of polyaryletherketoneresin overlying a substrate, in which topographical states of the layerof the polyaryletherketone resin represent data, the polyaryletherketoneresin comprising thermally cured one or more polyaryletherketonepolymers, each of the one or more polyaryletherketone polymers havingtwo terminal ends, each terminal end having two or more phenylethynylmoieties; a read-write head having one or more thermo-mechanical probes,each of the one or more thermo-mechanical probes including a resistiveregion for locally heating a tip of the thermo-mechanical probe inresponse to electrical current being applied to the one or morethermo-mechanical probes; and a scanning system for scanning theread-write head across a surface of the recording medium.

BRIEF DESCRIPTION OF DRAWINGS

The features of the invention are set forth in the appended claims. Theinvention itself, however, will be best understood by reference to thefollowing detailed description of an illustrative embodiment when readin conjunction with the accompanying drawings, wherein:

FIGS. 1A through 1C illustrate the structure and operation of a tipassembly for a data storage device including the data storage mediumaccording to the embodiments of the present invention;

FIG. 2 is an isometric view of a local probe storage array including thedata storage medium according to the embodiments of the presentinvention; and

FIG. 3 is a diagram illustrating formation of a curedpolyaryletherketone resin by cross-linking of reactive endgroups of apolyaryletherketone polymer according to embodiments of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A through 1C illustrate the structure and operation of a tipassembly 100 for a data storage device including the data storage mediumaccording to the embodiments of the present invention. In FIG. 1A, probetip assembly 100 includes a U-shaped cantilever 105 having flexiblemembers 105A and 105B connected to a support structure 110. Flexing ofmembers 105A and 105B provides for substantial pivotal motion ofcantilever 105 about a pivot axis 115. Cantilever 105 includes anindenter tip 120 fixed to a heater 125 connected between flexing members105A and 105B. Flexing members 105A and 105B and heater 125 areelectrically conductive and connected to wires (not shown) in supportstructure 110. In one example, flexing members 105A and 105B andindenter tip 120 are formed of highly-doped silicon and have a lowelectrical resistance, and heater 125 is formed of lightly doped siliconhaving a high electrical resistance sufficient to heat indenter tip 120,in one example, to between about 100° C. and about 500° C. when currentis passed through heater 125. The electrical resistance of heater 125 isa function of temperature.

Also illustrated in FIG. 1A is a storage medium (or a recording medium)130 comprising a substrate 130A, and a cured polyaryletherketone resinlayer 130B. In one example, substrate 130A comprises silicon. Curedpolyaryletherketone resin layer 130B may be formed by solution coating,spin coating, dip coating or meniscus coating polyaryletherketonepolymer and reactive diluent formulations and performing a curingoperation on the resultant coating. In one example, curedpolyaryletherketone resin layer 130B has a thickness between about 10 nmand about 500 nm. The composition of cured polyaryletherketone resinlayer 130B is described infra. An optional penetration stop layer 130Cis shown between cured polyaryletherketone resin layer 130B andsubstrate 130A. Penetration stop layer 130C limits the depth ofpenetration of indenter tip 120 into cured polyaryletherketone resinlayer 130B.

Turning to the operation of tip assembly 100, in FIG. 1A, an indentation135 is formed in cured polyaryletherketone resin layer 130B by heatingindenter tip 120 to a writing temperature T_(W) by passing a currentthrough cantilever 105 and pressing indenter tip 120 into curedpolyaryletherketone resin layer 130B. Heating indenter tip 120 allowsthe tip to penetrate the cured polyaryletherketone resin layer 130Bforming indentation 135, which remains after the tip is removed. In afirst example, the cured polyaryletherketone resin layer 130B is heatedby heated indenter tip 120, the temperature of the indenter tip beingnot greater than about 500° C., to form indentation 135. In a secondexample, the cured polyaryletherketone resin layer 130B is heated byheated indenter tip 120, the temperature of the indenter tip being notgreater than about 400° C., to form indentation 135. In a third example,the cured polyaryletherketone resin layer 130B is heated by heatedindenter tip 120, the temperature of the indenter tip being betweenabout 200° C. and about 500° C., to form indentation 135. In a fourthexample, the cured polyaryletherketone resin layer 130B is heated byheated indenter tip 120, the temperature of the indenter tip beingbetween about 100° C. and about 400° C., to form indentation 135. Asindentations 135 are formed, a ring 135A of cured polyaryletherketoneresin is formed around the indentation. Indentation 135 represents adata bit value of “1”, a data bit value of “0” being represented by anabsence of an indentation. Indentations 135 are nano-scale indentations(several to several hundred nanometers in width).

FIGS. 1B and 1C illustrate reading the bit value. In FIGS. 1B and 1C,tip assembly 100 is scanned across a portion of curedpolyaryletherketone resin layer 130B. When indenter tip 120 is over aregion of cured polyaryletherketone resin layer 130B not containing anindentation, heater 125 is a distance D1 from the surface of the curedpolyaryletherketone resin layer (see FIG. 1B). When indenter tip 120 isover a region of cured polyaryletherketone resin layer 130B containingan indentation, heater 125 is a distance D2 from the surface of thecured polyaryletherketone resin layer (see FIG. 1C) because the tip“falls” into the indentation. D1 is greater than D2. If heater 125 is ata temperature T_(R) (read temperature), which is lower than T_(W) (writetemperature), there is more heat loss to substrate 130A when indentertip 120 is in an indentation than when the tip is not. This can bemeasured as a change in resistance of the heater at constant current,thus “reading” the data bit value. It is advantageous to use a separateheater for reading, which is mechanically coupled to the tip butthermally isolated from the tip. A typical embodiment is disclosed inPatent Application EP 05405018.2, 13 Jan. 2005.

“Erasing” (not shown) is accomplished by positioning indenter tip 120 inclose proximity to indentation 135, heating the tip to a temperatureT_(E) (erase temperature), and applying a loading force similar towriting, which causes the previously written indent to relax to a flatstate whereas a new indent is written slightly displaced with respect tothe erased indent. The cycle is repeated as needed for erasing a streamof bits whereby an indent always remains at the end of the erase track.T_(E) is typically greater than T_(W). The erase pitch is typically onthe order of the rim radius. In a first example, the curedpolyaryletherketone resin layer 130B is heated by heated indenter tip120, the temperature of the indenter tip is not greater than about 500°C., and the erase pitch is 10 nm to eliminate indentation 135. In asecond example, the cured polyaryletherketone resin layer 130B is heatedby heated indenter tip 120, the temperature of the indenter tip is notgreater than about 400° C., and the erase pitch is 10 nm to eliminateindentation 135. In a third example, the cured polyaryletherketone resinlayer 130B is heated by heated indenter tip 120, the temperature of theindenter tip is between about 200° C. and about 400° C., and the erasepitch is 10 nm to eliminate indentation 135. In a fourth example, thecured polyaryletherketone resin layer 130B is heated by heated indentertip 120, the temperature of the indenter tip is between about 200° C.and about 500° C., and the erase pitch is 10 nm to eliminate indentation135.

FIG. 2 is an isometric view of a local probe storage array 140 includingthe data storage medium according to the embodiments of the presentinvention. In FIG. 2, local probe storage array 140 includes substrate145 having a cured polyaryletherketone resin layer 150 (similar to curedpolyaryletherketone resin layer 130B of FIGS. 1A, 1B and 1C), which actsas the data-recording layer. An optional tip penetration stop layer maybe formed between cured polyaryletherketone resin layer 150 andsubstrate 145. In one example, substrate 145 comprises silicon. Curedpolyaryletherketone resin layer 150 may be formed by solution coating,spin coating, dip coating or meniscus coating uncuredpolyaryletherketone resin formulations and performing a curing operationon the resultant coating. In one example, cured polyaryletherketoneresin layer 150 has a thickness between about 10 nm and about 500 nm anda root mean square surface roughness across a writeable region of curedpolyaryletherketone resin layer 150 of less than about 1.0 nm across thecured polyaryletherketone resin layer. The composition of curedpolyaryletherketone resin layer 150 is described infra. Positioned overcured polyaryletherketone resin layer 150 is a probe assembly 155including an array of probe tip assemblies 100 (described supra). Probeassembly 155 may be moved in the X, Y and Z directions relative tosubstrate 145 and cured polyaryletherketone resin layer 150 by anynumber of devices as is known in the art. Switching arrays 160A and 160Bare connected to respective rows (X-direction) and columns (Y-direction)of probe tip assemblies 100 in order to allow addressing of individualprobe tip assemblies. Switching arrays 160A and 160B are connected to acontroller 165 which includes a write control circuit for independentlywriting data bits with each probe tip assembly 100, a read controlcircuit for independently reading data bits with each probe tip assembly100, an erase control circuit for independently erasing data bits witheach probe tip assembly 100, a heat control circuit for independentlycontrolling each heater of each of the probe tip assembles 100, and X, Yand Z control circuits for controlling the X, Y and Z movement of probeassembly 155. The Z control circuit controls a contact mechanism (notshown) for contacting the cured polyaryletherketone resin layer 150 withthe tips of the array of probe tip assemblies 100.

During a write operation, probe assembly 155 is brought into proximityto cured polyaryletherketone resin layer 150 and probe tip assemblies100 are scanned relative to the cured polyaryletherketone resin layer.Local indentations 135 are formed as described supra. Each of the probetip assemblies 100 writes only in a corresponding region 170 of curedpolyaryletherketone resin layer 150. This reduces the amount of traveland thus time required for writing data.

During a read operation, probe assembly 155 is brought into proximity tocured polyaryletherketone resin layer 150 and probe tip assemblies 100are scanned relative to the cured polyaryletherketone resin layer. Localindentations 135 are detected as described supra. Each of the probe tipassemblies 100 reads only in a corresponding region 170 of curedpolyaryletherketone resin layer 150. This reduces the amount of traveland thus the time required for reading data.

During an erase operation, probe assembly 155 is brought into proximityto cured polyaryletherketone resin layer 150, and probe tip assemblies100 are scanned relative to the cured polyaryletherketone resin layer.Local indentations 135 are erased as described supra. Each of the probetip assemblies 100 reads only in a corresponding region 170 of curedpolyaryletherketone resin layer 150. This reduces the amount of traveland thus time required for erasing data.

Additional details relating to data storage devices described supra maybe found in the articles “The Millipede—More than one thousand tips forfuture AFM data storage,” P. Vettiger et al., IBM Journal of Researchand Development. Vol. 44 No. 3, May 2000 and “TheMillipede—Nanotechnology Entering Data Storage,” P. Vettiger et al.,IEEE Transaction on Nanotechnology, Vol. 1, No. 1, March 2002. See alsoU.S. patent Publication 2005/0047307, Published Mar. 3, 2005 to Frommeret al. and U.S. patent Publication 2005/0050258, Published Mar. 3, 2005to Frommer et al., both of which are hereby included by reference intheir entireties.

Turning to the composition of cured polyaryletherketone resin layer 130Bof FIGS. 1A through 1C, it should be understood that for the purposes ofthe present invention curing a polymer implies cross-linking the polymerto form a cross-linked polymer or resin.

The polyaryletherketone resin medium or imaging layer of the embodimentsof the present invention advantageously meets certain criteria. Thesecriteria include high thermal stability to withstand millions of writeand erase events, low wear properties (little or no pickup of materialby tips), low abrasion (tips do not easily wear out), low viscosity forwriting, glassy character with no secondary relaxations for long databit lifetime, and shape memory for erasability.

Cured polyaryletherketone resins according to embodiments of the presentinvention have high temperature stability while maintaining a low glasstransition temperature (Tg). In a first example, curedpolyaryletherketone resins according to embodiments of the presentinvention have a Tg of less than about 180° C. In a second example,cured polyaryletherketone resins according to embodiments of the presentinvention have a Tg of between about 100° C. and about 180° C.

The glass transition temperature should be adjusted for good writeperformance. To optimize the efficiency of the write process thereshould be a sharp transition from the glassy state to the rubbery state.A sharp transition allows the cured resin to flow easily when a hot tipis brought into contact and quickly return to the glassy state once thehot tip is removed. However, too high a T_(g) leads to high writecurrents and damage to the probe tip assemblies described supra.

A formulation of polyaryletherketone polymer according to embodiments ofthe present invention comprises one or more polyaryletherketonepolymers. Each of the polyaryletherketone polymers has the structure:

wherein R¹ is selected from the group consisting of:

wherein R² is selected from the group consisting of:

wherein R³ is selected from the group consisting ofpoly(arylacetylenes), poly(phenylethynyl),

wherein n is a integer from about 5 to about 50.

In a first example, polyaryletherketone polymers according toembodiments of the present invention advantageously have a molecularweight between about 3,000 Daltons and about 10,000 Daltons. In a secondexample, polyaryletherketone polymers according to embodiments of thepresent invention advantageously have a molecular weight between about4,000 Daltons and about 5,000 Daltons.

The endgroups R³ react during thermal curing with each other tocross-link the polyaryletherketone polymers into a polyaryletherketoneresin by cyclo-addition. Note endgroups (XV) and (XVI) are examples ofan endgroup having two phenylethynyl linkages that provide twocross-linking sites (as illustrated in FIG. 3). Endgroup (XVII) is anexample of a reactive endgroup having four phenylethynyl linkages thatprovides four cross-linking sites. Other phenylethynyl containingendgroups having two or more phenylethynyl moieties may be substitutedfor endgroups (XIV), (XVI) and (XVII).

FIG. 3 is a diagram illustrating formation of a curedpolyaryletherketone resin by cross-linking of reactive endgroups of apolyaryletherketone polymer according to embodiments of the presentinvention. In FIG. 3, a straight chain polyaryletherketone polymer 250of repeating units n and having two endgroups 255, each having twophenylethynyl moieties 260 is heat cured to produce a cross-linkedpolyaryletherketone resin 265. In polyaryletherketone resin 265,polyaryletherketone polymers 250 are linked to each other throughrespective phenylethynyl moieties 260 of reactive endgroups 255.Cross-linking of polyaryletherketone polymers 250 in polyaryletherketoneresin 265 is by cyclo-addition of the phenylethynyl moieties 260.

In FIG. 3, only cross-linking of two phenylethynyl groups on the ends oftwo different polymer has been illustrated. It should be understood thatthree or more phenylethynyl groups, each on a end of a differentpolymer, can react by cascading cyclo-addition so that three or morepolymer ends are cross-linked at a single point.

SYNTHESIS EXAMPLES

All materials were purchased from Aldrich and used without furtherpurification unless otherwise noted.

Synthesis of the Reactive Endgroup3,5-bis(4-(phenylethynyl)phenyl)phenol (Structure XV):

(i) Synthesis of 4-(phenylethynyl)-1-bromobenzene (JACS, 2004, 126,4540): 1-Bromo-4-iodobenzene (20.0 g, 70.7 mmol),bis(triphenylphospine)palladium(II) dichloride (PdCl₂(PPh₃)₂) (250 mg),and CuI (68 mg) were suspended in 50 mL triethylamine (NEt₃) and 100 mLtetrahydrofuran (THF). The suspension was treated with 3 cycles ofevacuation and refilling with N₂. Phenylacetylene (7.21 g, 7.75 mL, 1.0eq) was added in 0.5 mL portions every 5 minutes to the stirredsuspension. The solution was then stirred at room temperature for 22hours. The solvents were then evaporated. Methylene chloride (100 mL)and 1 M HCl (aqueous) (50 mL) were added, the organic layer wasretained, and then was washed again with 1 M HCl (aqueous) (50 mL) and2×50 mL water, dried (MgSO₄), filtered, and the solvent evaporated invacuum to give 18 g of the title compound as a yellow solid, which wasused without further purification.

(ii) Synthesis of 4-(phenylethynyl)phenyl boronic acid (JACS, 2004, 126,5798): In a flame-dried flask, 4-(phenylethynyl)-1-bromobenzene (15.0 g,58.4 mmol) was dissolved in dry THF (225 mL). The solution was treatedwith 3 cycles of evacuation and refilling with N₂, then chilled to −78°C. in a dry ice/acetone bath. To the stirred solution was added asolution of n-butyllithium in hexanes (1.6 M, 40 mL, 1.1 eq) by syringeover the course of 10 minutes. The resulting solution was stirred for anadditional 30 minutes before trimethylborate (9.77 mL, 9.1 g, 1.5 eq)was added slowly over 15 minutes. After stirring for an additional 15minutes, the cooling bath was removed and the solution was allowed towarm to room temperature and stir for 16 h. At this time, 2 M HCl(aqueous) (375 mL) was added, and the biphasic system was stirredvigorously for 2 hours. Ethyl acetate was added, and the organic layerwas separated, dried (MgSO₄), filtered and evaporated. Methylenechloride (100 mL) was added to the solid residue, which was crushed andmixed into a paste, then filtered and washed with additional portions ofmethylene chloride to give 8.5 g of the title compound as a whitepowder.

(iii) Synthesis of 3,5-bis(4-(phenylethynyl)phenyl)phenol:4-(Phenylethynyl)phenyl boronic acid (4.65 g, 20.9 mmol) was dissolvedin 100 mL of toluene/ethanol (4:1 (v/v)), 3,5-dibromophenol (2.52 g, 10mmol) was added, and then 20 mL of 2 M Na₂CO₃ (aqueous) was added. Theresulting mixture was treated with 3 cycles of evacuation and refillingwith N₂. Solid tetrakis(triphenylphospine)palladium(II) (Pd(PPh₃)₄) (232mg) was then added, followed by 3 more cycles of evacuation andrefilling with N₂. The reaction mixture was then heated to 85° C. in anoil bath for 5 hours. The reaction was cooled, and water (100 mL) andmethylene chloride (100 mL) were added. The organic layer was separated,washed with water (50 mL), then dried (MgSO₄), filtered, and evaporated.The crude product was purified by column chromatography (silica, CH₂Cl₂)or alternately by trituration with CH₂Cl₂ followed by filtration to givein either case about 2.5 g of the title compound as a white solid.

Example Synthesis of a Polyaryletherketone Polymer (Structure XVIII):

In a multi-necked flask equipped with a mechanical stirring apparatusand a Dean-Stark trap, 4,4′-difluorobenzophenone (1.4187 g, 6.502 mmol),resorcinol (0.6658 g, 6.047 mmol),3,5-bis(4-(phenylethynyl)phenyl)phenol (403.1 mg, 0.9037 mmol), andpotassium carbonate (3 g, 22 mmol) were suspended in a mixture of DMF(10 mL) and toluene (20 mL). The reaction mixture was vigorously stirredand heated to 130° C. for 16 hours under a slow flow of dry nitrogen,and toluene was removed periodically via the Dean-Stark trap. At the endof the 16 hour period, the temperature was increased to 150° C. foranother 8 hours. The reaction was then cooled and the polymer wasisolated by multiple precipitations using THF and methanol. Molecularweights were adjusted by using different proportions of monomers andendcaps and several different molecular weight polymers were prepared.

Thus, the embodiments of the present invention provide for compositionsof matter for the storage media that operate in the nanometer regime.

The description of the embodiments of the present invention is givenabove for the understanding of the present invention. It will beunderstood that the invention is not limited to the particularembodiments described herein, but is capable of various modifications,rearrangements and substitutions as will now become apparent to thoseskilled in the art without departing from the scope of the invention.Therefore, it is intended that the following claims cover all suchmodifications and changes as fall within the true spirit and scope ofthe invention.

1. A method, comprising: forming a layer of one or morepolyaryletherketone polymers on a substrate; thermally curing said layerof one or more polyaryletherketone polymers of form a resin layer ofpolyaryletherketone resin, said polyaryletherketone resin cross-linkedby cyclo-addition reactions of phenylethynyl moieties; heating andbringing a thermo-mechanical device into contact with said resin layerto write information into said resin layer by forming depressions insaid resin layer; bringing said thermo-mechanical device, when unheated,into proximity to said resin layer to read information stored in saidresin layer; heating and bringing said thermo-mechanical device intoproximity with said resin layer to erase information from said resinlayer by reflowing said depressions; each polyaryletherketone polymer ofsaid one or more polyaryletherketone polymers having two terminal ends,each terminal end having two or more phenylethynyl moieties; whereinsaid polyaryletherketone resin has a glass transition temperature ofbetween about 100 ° C. and about 180 ° C.; wherein eachpolyaryletherketone polymer of said one or more polyaryletherketonepolymers has the structure:

wherein R¹ is selected from the group consisting of:

wherein R² is selected from the group consisting of:

wherein R³ is selected from the group consisting ofpoly(arylacetylenes), poly(phenylethynyl),

wherein n is a integer from about 5 to about 50; and wherein each ofsaid one or more polyaryletherketone polymers has a molecular weightbetween about 3.000 Daltons and about 10.000 Daltons. 2-30. (canceled)